Around 12:40 p.m. base emergency personnel responded to the Wright-Patterson Medical Center after a report of an active shooter, officials said.

An unknown individual called 911 believing an active shooter drill was the real thing, prompting security forces to descend on the hospital building and sweep to clear the hospital, base officials said in a statement.

There was no shooter, but a firearm was discharged.

"In an attempt to breach a door that was locked, a securty forces member discharged his firearm to open the door and continue the sweep," officials said.

By around 2:30 p.m. an all-clear was issued, but security advised base personnel to avoid the hospital.

Olen Kelley III was on his way to the gym Thursday when he saw a stream of about 100 law enforcement and emergency vehicles rushing toward the base.

The Air Force veteran with more than 20 years of service immediately called his wife who works on the base. She didn’t pick up.

He stopped and then heard the reports of an active shooter, news he said was later confirmed by a uniformed officer. Kelley started to worry.